A complicated weather situation was found during the afternoon of the 8th.  A large upper level low pressure system was positioned over the western U.S. with a broad south to southwest flow of air over the middle of the nation.  Surface low pressure moved across South Dakota during the afternoon.  A dry line extended south from the low and tracked across Nebraska.  At the same time, a vorticity maximum lifted northeast from Oklahoma into Iowa during the late afternoon hours.  Convergence and lift were both enhanced by these features.  The airmass became quite unstable during the afternoon, especially over the west half of Iowa.  Surface temperatures warmed into the low to mid 80s as dew point readings reached the low 60s.  By mid afternoon, the lifted index fell to around -9 C with no cap in place and 2000 to 3000 J/kg of CAPE.  The freezing level was relatively low, being just below 12,000 feet at the beginning of the event.  Cold air advection took place aloft, lowering the freezing level to 11,000 by late afternoon.  Three areas of thunderstorms developed.  The dry line kicked off a line of severe thunderstorms to the west of Iowa.  These storms did not directly affect Iowa, however they did enhance convergence in the flow.  A second area formed over western Iowa as the airmass became very unstable.  Thunderstorms erupted by mid afternoon.  Many of them produced hail of three quarters of an inch to an inch in diameter.  Hail covered the ground in a few locations.  In Emmet County, the town of Ringsted received hail of 2 inches in diameter.  There were some reports of gusty winds with the storms, however winds of severe strength were limited.  Seventy MPH winds were reported west of Breda in Carroll County.  In Palo Alto County, a 73 MPH wind gust was measured in the town of Mallard.  These storms formed in a northeast to southwest line and trained over areas of northwest Iowa.  This resulted in flash flooding in Pocahontas and parts of Kossuth Counties.  Two to two and one half inches of rain fell in about an hour in these areas.  These were the same areas that received heavy rainfall just 48 hours prior.  Water overtopped roads countywide in Pocahontas County.  Flooding was less severe in Kossuth County, however the flooding took place in and around the town of Algona.  The short wave lifting north from Oklahoma produced convection.  Though the convection was not severe, it did aid in the production of a high wind event.  The storms moved into Iowa and collapsed, producing an outflow that expanded north across the central counties.  Winds of 35 to 40 MPH, with gusts to over 60 MPH pushed north across several counties in the central sections of the state.  The winds caused considerable blowing dust in these areas and there were numerous reports of trees being blown down.  In Story County, two to three foot diameter trees were toppled.  One of them fell onto a house in Huxley, causing considerable damage to the house.

Hail in SAC, IOWA
From 08-MAY-05 14:45:00 to 08-MAY-05 14:45:00 (CST)
Location: WALL LAKE MUNI ARPT
Magnitude: 0.88 
Property damage: 1K
Reported by: TRAINED SPOTTER

Hail in CRAWFORD, IOWA
From 08-MAY-05 15:06:00 to 08-MAY-05 15:06:00 (CST)
Location: CHARTER OAK
Magnitude: 1.00 
Property damage: 5K
Reported by: TRAINED SPOTTER

Hail in POCAHONTAS, IOWA
From 08-MAY-05 15:20:00 to 08-MAY-05 15:20:00 (CST)
Location: PALMER
Magnitude: 0.88 
Property damage: 1K
Reported by: TRAINED SPOTTER

Hail in PALO ALTO, IOWA
From 08-MAY-05 15:33:00 to 08-MAY-05 15:33:00 (CST)
Location: MALLARD
Magnitude: 1.00 
Property damage: 5K
Reported by: TRAINED SPOTTER

Hail in CRAWFORD, IOWA
From 08-MAY-05 15:39:00 to 08-MAY-05 15:39:00 (CST)
Location: VAIL
Magnitude: 0.75 
Reported by: TRAINED SPOTTER

Thunderstorm Wind in CARROLL, IOWA
From 08-MAY-05 15:42:00 to 08-MAY-05 15:42:00 (CST)
Location: BREDA
Magnitude: 61 EG
Property damage: 2K
Reported by: TRAINED SPOTTER

Hail in PALO ALTO, IOWA
From 08-MAY-05 15:53:00 to 08-MAY-05 15:53:00 (CST)
Location: EMMETSBURG
Magnitude: 1.00 
Property damage: 2K
Reported by: BROADCAST MEDIA

Hail in EMMET, IOWA
From 08-MAY-05 16:15:00 to 08-MAY-05 16:15:00 (CST)
Location: RINGSTED
Magnitude: 0.75 
Reported by: TRAINED SPOTTER

Hail in EMMET, IOWA
From 08-MAY-05 16:19:00 to 08-MAY-05 16:19:00 (CST)
Location: RINGSTED
Magnitude: 2.00 
Property damage: 25K
Reported by: TRAINED SPOTTER

Hail in EMMET, IOWA
From 08-MAY-05 16:24:00 to 08-MAY-05 16:24:00 (CST)
Location: RINGSTED
Magnitude: 0.88 
Property damage: 1K
Reported by: EMERGENCY MANAGER

Hail in KOSSUTH, IOWA
From 08-MAY-05 16:33:00 to 08-MAY-05 16:33:00 (CST)
Location: WHITTEMORE
Magnitude: 0.75 
Reported by: TRAINED SPOTTER

Hail in KOSSUTH, IOWA
From 08-MAY-05 16:43:00 to 08-MAY-05 16:43:00 (CST)
Location: LAKOTA
Magnitude: 0.88 
Property damage: 1K
Reported by: FIRE DEPT/RESCUE SQUAD

Hail in HUMBOLDT, IOWA
From 08-MAY-05 16:46:00 to 08-MAY-05 16:46:00 (CST)
Location: BRADGATE
Magnitude: 0.88 
Property damage: 1K
Reported by: TRAINED SPOTTER

Thunderstorm Wind in HANCOCK, IOWA
From 08-MAY-05 17:30:00 to 08-MAY-05 17:30:00 (CST)
Location: KANAWHA
Magnitude: 50 EG
Property damage: 1K
Reported by: LAW ENFORCEMENT

High Wind in BOONE, IOWA
From 08-MAY-05 15:30:00 to 08-MAY-05 17:00:00 (CST)
Magnitude: 35 ES
Property damage: 10K
Reported by: AWOS,ASOS,MESONET,ETC

High Wind in HAMILTON, IOWA
From 08-MAY-05 15:30:00 to 08-MAY-05 17:00:00 (CST)
Magnitude: 50 MG
Property damage: 10K
Reported by: AWOS,ASOS,MESONET,ETC

High Wind in JASPER, IOWA
From 08-MAY-05 15:30:00 to 08-MAY-05 17:00:00 (CST)
Magnitude: 53 MG
Property damage: 20K
Reported by: AWOS,ASOS,MESONET,ETC

High Wind in STORY, IOWA
From 08-MAY-05 15:30:00 to 08-MAY-05 17:00:00 (CST)
Magnitude: 57 EG
Property damage: 50K
Reported by: TRAINED SPOTTER

High Wind in WEBSTER, IOWA
From 08-MAY-05 15:30:00 to 08-MAY-05 17:00:00 (CST)
Magnitude: 52 EG
Property damage: 15K
Reported by: TRAINED SPOTTER

Flash Flood in POCAHONTAS, IOWA
From 08-MAY-05 16:34:00 to 08-MAY-05 20:30:00 (CST)
Location: COUNTYWIDE
Property damage: 25K
Reported by: BROADCAST MEDIA

Flash Flood in KOSSUTH, IOWA
From 08-MAY-05 17:00:00 to 08-MAY-05 20:46:00 (CST)
Location: ALGONA
Property damage: 25K
Reported by: TRAINED SPOTTER

Thunderstorm Wind in PALO ALTO, IOWA
From 08-MAY-05 15:51:00 to 08-MAY-05 15:51:00 (CST)
Location: MALLARD
Magnitude: 63 MG
Property damage: 5K
Reported by: AWOS,ASOS,MESONET,ETC

Hail in KOSSUTH, IOWA
From 08-MAY-05 16:40:00 to 08-MAY-05 16:40:00 (CST)
Location: LAKOTA
Magnitude: 1.00 
Property damage: 3K
Reported by: TRAINED SPOTTER